1. Field of the Invention
This invention relates generally to drive mechanisms for converting rotary motion to reciprocating motion and more particularly to the conversion of a uniform speed rotary motion to a rapid advance stroke and slow return stroke of the reciprocating component and to the adaptation of such drive mechanisms to multiple slide machines used in forming metal wire or ribbon into a wide variety of products.
2. Description of the Prior Art
Multiple slide machines, also known as four-slide machines, provide the various basic motions required to form lengths of wire or ribbon into a variety of metal products in a wide range of sizes and configurations. The cycle of operation of these machines comprises the four general steps of feeding a predetermined length of wire into the forming mechanism, cutting the length from the supply reel, forming the cut length by operation of the slides and then ejecting the finished piece. Each revolution of the main drive shaft, which includes four component shafts mounted along the periphery of the rectangular bed of the machine, performs one complete cycle of operation through appropriate actuation of the slides and a rotary to reciprocating motion conversion drive mechanism operating a precision reciprocating wire or ribbon feeder which performs the measuring and feeding step. The feeder has a gripper which reciprocates along a straight track provided with adjustable abutment stops at each opposite end to limit the length of travel of the gripper to a close tolerance and hence provide for precise measurement of the wire being fed. The conventional rotary to reciprocating motion conversion drive mechanism heretofore provided in multiple slide machines requires the forward and return strokes of the gripper to be of equal time duration, the wire being gripped and advanced into the bed of the machine during the forward stroke while the slides are at rest in a dwell period of one half cycle. During the other half cycle the gripper releases the wire and returns while the cutting and forming operations are being performed by the slides.
The need for increasing the time in each cycle during which the slides are in operation by shortening the time interval of the feed stroke in order to achieve maximum output of the machine has long been recognized, particularly where the piece is formed from a relatively short length of wire or ribbon stock, such as 11/2 to 2 inches. One solution in prior use provides a rapid feed device which occupies one of the slide positions and hence reduces the forming capability of the machine to that of the three remaining slides. Another prior art device utilizes two rapid feed strokes for each cycle while increasing the forming operation time interval of each cycle. But this mechanical arrangement is utilized for relatively low output with upper limits of approximately 160 units per minute and where the length of wire required for each unit may approach 20 inches so that two short rapid feed strokes have advantages over one long stroke. The latter arrangement is not feasible for high speed machines capable of maximum output of 550 units per minute when forming such units from stock 11/2 to 2 inches in length.